Nitrous oxide
Nitrous oxide makes up an extremely small amount of the Atmosphere - it is less than one-thousandth as abundant as carbon dioxide. However, per molecule, it is 200 to 300 times more effective in trapping heat than carbon dioxide.
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[edit] Sources of Nitrous oxide
[edit] Natural
Natural sources of nitrous oxide are dominated by temperate and tropical soils, with the world's oceans also being an important contributor. Total annual emissions of N2O from natural sources are etimated to be about 10 million tonnes of N2O-N.
[edit] Human-made
The human-made (anthropogenic) emission of N2O is of a similar magnitude to natural sources. Here, agricultural soils are by far the biggest source. When nitrogen-rich Fertilizers are added to fields, some of the nitrogen can end up being emitted as N2O through the processes of nitrification and denitrification. Both these processes are usually a result of microorganisms (nitrifiers and denitrifiers). Nitrification is common where the soil is well aerated, while denitrification tends to predominate where the Soils are more water-logged and the supply of Oxygen is limited. Globally, between 2 and 4 million tonnes of N2O-N are thought to be released into the atmosphere each year via this pathway.
Industry, in particular the production of nitrogen fertilizers and nylon, is an important source of global N2O emissions, as is fossil fuel burning in power generation. Other important human-made sources of N2O include biomass burning, cattle and cattle feed production.
[edit] The natural nitrous oxide cycle
Nitrogen is removed from the atmosphere by plants and converted into forms such as ammonia, which can then be used by the plants. This is called nitrogen fixation. At the same time, micro-organisms remove nitrogen from the soil and put it back into the atmosphere - denitrification - and this process produces nitrous oxide. Nitrous oxide also enters the atmosphere from the ocean.
Nitrous oxide has one of the longest Atmosphere lifetimes of the greenhouse gases, lasting for up to 150 years.
[edit] The impact of human activities
Burning Fossil fuels and wood is one source of the increase in atmospheric nitrous oxide, however the main contributor is believed to be the widespread use of nitrogen-base Fertilisers. Sewage treatment plants may also be a major source of this gas.
[edit] The statistics
Since the Industrial Revolution, the level of nitrous oxide in the atmosphere has increased by 16%.
[edit] Nitrous Oxide Is Destroying the Earth
Sure whipits are fun, but now nitrous is destroying a lot more than your brain cells. A study published today in Science proves it is the leading cause of Ozone layer destruction in the twenty-first century.
Back in the good old days, kids inhaled nitrous oxide out of whip cream canisters without a care in the world. But, according to geochemist A.R. Ravishankara, "manmade nitrous oxide is now the elephant in the room among ozone-depleting substances." It causes more ozone destruction in the upper atmosphere than any other form of emission - and according to the atmospheric models created by Ravishankara and his team, the gas is likely to linger in the atmosphere for the rest of the century.
According to their study, nitrous oxide is dangerous because it comes from natural sources as well as human-made ones:
Nitrous oxide is emitted from livestock manure, sewage treatment, combustion and certain other industrial processes. Dentists use it as a sedative (so-called "laughing gas"). In nature, Bacteria in Soil and the oceans break down nitrogen-containing compounds, releasing nitrous oxide. About one-third of global nitrous oxide emissions are from human activities. Nitrous oxide, like chlorofluorocarbons, is stable when emitted at ground level, but breaks down when it reaches the stratosphere to form other gases, called nitrogen oxides, that trigger Ozone-destroying reactions.
So now you know. Every hit you take on that nitrous cracker is killing the Earth.
[edit] Natural Sources - Global Emissions
Natural emissions of N2O primarily result from bacterial breakdown of nitrogen in soils and in the earth's oceans. Globally, soils covered by natural vegetation are estimated to produce 6.6 Tg of N2O annually and oceans are thought to add around 5.4 Tg of N2O annually to the atmosphere (U.S. EPA). Together, these two sources account for over 90 percent of the natural sources. Nitrous oxide is also produced in smaller quantities from chemical reactions in the Atmosphere. In some ocean areas, large areas of surface water can become Oxygen depleted, allowing active denitrification in open water. Large amounts of oceanic nitrous oxide can also arise from denitrification in marine sediments, particularly in nutrient rich areas such as those of estuaries.
It is important in studies of N2O emissions to account for the various interactions between natural processes and human influences in the nitrogen cycle, since human impacts can significantly enhance the natural processes that lead to N2O formation. For example, the nitrogen nutrient loading in water bodies due to fertilization and run-off to streams can enhance N2O emissions from these natural sources. Human-related ammonia emissions have also been shown to cause N2O emissions in the atmosphere through Ammonia oxidation.
[edit] The future
Due to the long time it spends in the Atmosphere, the nitrous oxide that we release today will still be trapping heat well into the next century.
